How do restriction enzymes cut $DNA$ sequences?

• A. By recognizing specific nucleotide sequences and cleaving the $DNA$ at those sites
• B. By randomly cutting $DNA$ at any location
• C. By binding to $RNA$ and then cutting $DNA$
• D. By altering the $DNA$ sequence before cutting

Answer: (A)

Verified step by step guidance

1. Understand that restriction enzymes are proteins used by bacteria to protect against viral DNA by cutting it at specific sites.
2. Learn that these enzymes recognize specific sequences of nucleotides in the DNA, known as recognition sites, which are typically palindromic.
3. Know that once the restriction enzyme binds to its recognition site, it cleaves the DNA at or near this site, creating fragments with 'sticky' or 'blunt' ends.
4. Realize that the specificity of restriction enzymes is due to their ability to form hydrogen bonds with the specific nucleotide sequences, ensuring precise cutting.
5. Remember that restriction enzymes do not alter the DNA sequence before cutting; they only recognize and cleave at specific sites.